Plant and environmental sensory signals control the expression of hrp genes in Pseudomonas syringae pv. phaseolicola.

The hrp genes of Pseudomonas syringae pv. phaseolicola control the development of primary disease symptoms in bean plants and the elicitation of the hypersensitive response in resistant plants. We examined the expression of the seven operons located in the 22-kb hrp cluster (L. G. Rahme, M. N. Mindrinos, and N. J. Panopoulos, J. Bacteriol. 173:575-586, 1991) in planta and in vitro under different physiological and nutritional conditions by using chromosomally located hrp::inaZ reporter fusions. We show that (i) a plant signal(s) is specifically required for the induction of the seven hrp operons, during both compatible and incompatible interactions; (ii) hrpL and hrpRS are regulated by different mechanisms in planta and in vitro; and (iii) expression of individual hrp loci is differentially affected by pH, osmotic strength, and type of carbon source: hrpAB, hrpC, and hrpD were downregulated similarly by osmolarity, pH, and certain carbon sources; hrpE expression was affected strongly by pH and carbon substrate and slightly by osmolarity; and hrpF was not substantially affected by any of these factors. These findings suggest complex signaling mechanisms taking place during plant-pathogen interactions.     

Hardening, abscisic acid, proline and freezing resistance in two winter wheat varieties

Two varieties of winter wheat ( Triticum aestivum L.) differing in freezing resistance ("Holme" from Sweden, freezing resistant, and "Amandus" from Germany, less freezing resistant) were hardened for five weeks by gradually reducing the day/night temperature from 20°C/15°C during the first week to 2° C/0° C during the fifth week and the photoperiod from 15 to 9 h. This treatment increased the freezing resistance of both varieties in comparison to unhardened control plants. Hardening caused an increase in osmolarity of cell sap and in the levels of proline and abscisic acid (ABA). Increase in osmolarity preceded the increase in ABA level, and proline levels increased later than ABA levels. Holme had higher values of osmolarity as well as higher levels of ABA and proline. but the differences between the two varieties were significant only for proline. Since the pressure potential remained constant or increased slightly during the hardening period, it is suggested that the accumulation of ABA is due to the hardening process and not to simple water stress caused by cold-induced inhibition of water uptake by the root.
Spraying hardened plants with 10⁻⁴ M ABA 24 h before a freezing test increased freezing resistance in both varieties, but did not obliterate the differences in freezing resistance between the two varieties. Spraying hardened plants with an aqueous proline solution (10%, w/v) was without effect on freezing resistance. It is concluded that the hardening procedure causes an accumulation of ABA in winter wheat leaves and that ABA is involved in the chain of events leading to freezing resistance.     

The effect of water acidification on prolactin cells and pars intermedia PAS-positive cells in the teleost fish Oreochromis (formerly Sarotherodon) mossambicus and Carassius auratus

Summary Although exposure to acid water (pH 3.5) induces severe and prolonged reduction in plasma osmolarity and total plasma calcium concentration in tilapia (Oreochromis mossambicus) and goldfish (Carassius auratus), the responses of the hypophyseal cells are clearly different. In tilapia, the size of the rostral pars distalis of the pituitary gland is enlarged as a result of the increase in size and number of prolactin cells. The pars intermedia PAS-positive (PIPAS) cells are not noticeably changed. Conversely, in goldfish, prolactin cells are unaffected, whereas the number of enlarged PIPAS cells increases markedly. Stimulation of prolactin secretion may be responsible for the partial restoration of plasma osmolarity and calcium levels observed in tilapia after two weeks exposure to acid water. Prolactin cells apparently play a role in the adaptation to acid stress by counteracting osmoregulatory disturbances. Goldfish show no restoration of plasma osmolarity during the course of the experiment. Plasma calcium levels tend to increase. Although prolactin may have an osmoregulatory function in goldfish under steady state conditions, goldfish prolactin cells do not seem to participate in the physiological adaptation to environmental changes that disturb water and ion homeostasis. The function of PIPAS cells in tilapia remains unclear and is apparently unconnected with ion regulation. The observations on these cells in goldfish are consistent with the hypercalcemic activity suggested for them.     

日本沼虾雄性生殖细胞原代培养方法

细胞培养方法对于研究虾类疾病、内分泌生理是一种有力的工具。本文介绍了日本沼虾(Macrobrachium nipponense)雄性生殖细胞原代培养的方法。实验发现精原细胞和精母细胞在体外具有较强的分裂能力。通过测定细胞的贴壁率及观察细胞生长情况,初步确定了该类细胞体外培养的最适pH范围为7.2~7.4,渗透压范围为400~500mmol/L。     

Olive fruit fly (Diptera: Tephritidae) ovipositional preference and larval performance in several commercially important olive varieties in California

The olive fruit fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae),is an invasive pest of olives (Olea spp.) in the United States. The objectives of this study were to determine whether B. oleae exhibits ovipositional preference under California field conditions similar to that demonstrated in European populations and whether the resulting larvae fare better in preferred varieties. Female B. oleae exhibited strong ovipositional preference for certain varieties of the domesticated olive, Olea europaea L, and the resulting larvae performed better by some measures in preferred varieties than in lesser preferred varieties. Ovipositional preference was observed in the field from 2003 to 2005, and laboratory assays were conducted to evaluate larval performance in 2005 and 2006. Among the olive varieties tested, Sevillano, Manzanillo, and Mission olives were the most heavily infested during three consecutive years. The larval performance measurements used were pupal yield, pupal weight, larval developmental time, and pupal emergence time. Ovipositional preference and pupal yield do not seem associated. There were significant differences in pupal emergence time, but these also measures did not reflect ovipositional preference. Two measures on performance did seem related to ovipositional preference; there were significant effects of variety on pupal weight and larval developmental time. Pupae developing in Manzanillo and Sevillano olives were heavier than those developing in less preferred varieties, and larval developmental time was significantly shorter in Sevillano olives relative to the other varieties. Oviposition preference and enhanced larval performance has implications for the pest status of this invasive insect in California.     

Murine macrophage lysozyme: modulation of enzymatic activity in gel by electrolytes.

Enzymatic activity of macrophage lysozyme in gels under normal physiological conditions of ionic strength, osmolarity, temperature and pH is negligible. Under isotonic conditions macrophage lysozyme can attain maximum activity at acid pH (acid lysozyme). At neutral and alkaline pH macrophage lysozyme can be fully activated by lowering the osmolarity to 155 imOsm (alkaline lysozyme). Such modulation of enzymatic activity is not seen when macrophage lysozyme is assayed in solution. The different behavior of macrophage lysozyme in solution and in gel is briefly discussed in terms of lysozyme function in intact cells.     

Characteristics and osmoregulatory roles of uptake systems for proline and glycine betaine in Lactococcus lactis.

Lactococcus lactis subsp. lactis ML3 contains high pools of proline or betaine when grown under conditions of high osmotic strength. These pools are created by specific transport systems. A high-affinity uptake system for glycine betaine (betaine) with a Km of 1.5 microM is expressed constitutively. The activity of this system is not stimulated by high osmolarities of the growth or assay medium but varies strongly with the medium pH. A low-affinity proline uptake system (Km, > 5 mM) is expressed at high levels only in chemically defined medium (CDM) with high osmolarity. This transport system is also stimulated by high osmolarity. The expression of this proline uptake system is repressed in rich broth with low or high osmolarity and in CDM with low osmolarity. The accumulated proline can be exchanged for betaine. Proline uptake is also effectively inhibited by betaine (Ki of between 50 and 100 microM). The proline transport system therefore probably also transports betaine. The inhibition of proline transport by betaine results in low proline pools in cells grown in high-osmotic-strength, betaine-containing CDM. The energy and pH dependency and the influence of ionophores on the activity of both transport systems suggest that these systems are not proton motive force driven. At low osmolarities, proline uptake is low but significant. This low proline uptake is also inhibited by betaine, although to a lesser extent than in cells grown in high-osmotic-strength CDM. These data indicate that proline uptake in L. lactis is enzyme mediated and is not dependent on passive diffusion, as was previously believed.     

Isosmotic volume reabsorption in rat proximal tubule

A theoretical model incorporation both active and passive forces has been developed for fluid reabsorption from split oil droplets in rat intermediate and late proximal tubule. Of necessity, simplifying assumptions have been introduced; we have assumed that the epithelium can be treated as a single membrane and that the membrane "effective" HCO3 permeability is near zero. Based on this model with its underlying assumptions, the following conclusions are drawn. Regardless of the presence or absence of active NaCl transport, fluid reabsorption from the split oil droplet is isosmotic. The reabsorbate osmolarity can be affected by changes in tubular permeability parameters and applied forces but is not readily altered from an osmolarity essentially equal to that of plasma. In a split droplet, isosmotic flow need not be a special consequence of active Na transport, is not the result of a particular set of permeability properties, and is not merely a trivial consequence of a very high hydraulic conductivity; isosmotic flow can be obtained with hydraulic conductivity nearly an order of magnitude lower than that previously measured in the rat proximal convoluted tubule. Isosmotic reabsorption is, in part, the result of the interdependence of salt and water flows, their changing in parallel, and thus their ratio, the reabsorbate concentration being relatively invariant. Active NaCl transport can cause osmotic water flow by reducing the luminal fluid osmolarity. In the presence of passive forces the luminal fluid can be hypertonic to plasma, and active NaCl transport can still exert its osmotic effect on volume flow. There are two passive forces for volume flow: the Cl gradient and the difference in effective osmotic pressure; they have an approximately equivalent effect on volume flow. Experimentally, we have measured volume changes in a droplet made hyperosmotic by the addition of 50 mM NaCl; the experimental results are predicted reasonably well by our theoretical model.     

Decomposition of ethylene,a flower-senescence hormone,with electrolyzed anode water

Electrolyzed anode water (EAW) markedly extended the vase life of cut carnation flowers. Therefore, a flower-senescence hormone involving ethylene decomposition by EAW with potassium chloride as an electrolyte was investigated. Ethylene was added externally to EAW, and the reaction between ethylen and the available chlorine in EAW was examined. EAW had a low pH value (2.5), a high concentration of dissolved oxygen, and extremely high redox potential (19.2 mg/l and 1323 mV, respectively) when available chlorine was at a concentration of about 620 microns. The addition of ethylene to EAW led to ethylene decomposition, and an equimolar amount of ethylene chlorohydrine with available chlorine was produced. The ethylene chlorohydrine production was greatly affected by the pH value (pH 2.5, 5.0 and 10.0 were tested), and was faster in an acidic solution. Ethylene chlorohydrine was not produced after ethylene had been added to EAW at pH 2.6 when available chlorine was absent, but was produced after potassium hypochlorite had been added to such EAW. The effect of the pH value of EAW on the vase life of cut carnations was compatible with the decomposition rate of ethylene in EAW of the same pH value. These results suggest that the effect of EAW on the vase life of cut carnations was due to the decomposition of ethylene to ethylene chlorohydrine by chlorine from chlorine compounds.     

The effect of pH and/or calcium-enriched freshwater on gill Ca2+-ATPase activity and osmotic water inflow in rainbow trout (Salmo gairdneri)

Rainbow trout (Salmo gairdneri) were exposed to pH 5.0-5.1, 6.6 and/or calcium-enriched freshwater for 14 days. Hematocrit, gill Ca2+-ATPase enzyme activities, gill osmotic water inflow, plasma calcium and osmolarity were measured. No significant changes in plasma calcium ion levels were found. The typical increase in hematocrit usually associated with exposure of fish to acidified water was not found in the present study and is discussed. Plasma osmolarity decreased in fish exposed to calcium-enriched freshwater (60 mg Ca2+ X 1(-1) ) in comparison to fish exposed to control freshwater conditions (2 mg Ca2+ X 1(1) ), irrespective of the pH level. Gill Ca2+-ATPase enzyme activities were measured for both low affinity (3 mM Ca2+) and high affinity (100 microM) activity. Exposure of rainbow trout to low pH (pH 5.0-5.1) did not affect the specific activity of Ca2+-ATPase enzyme. However, low affinity Ca2+-ATPase activity in fish exposed to calcium-enriched freshwater did show a significant reduction. The increase in gill osmotic water permeability in fish exposed to calcium-enriched freshwater is interpreted as a result of the increase in osmolarity of the ambient media.     

The behavior of 9-aminoacridine as an indicator of transmembrane pH difference in liposomes of natural bacterial phospholipids

The behavior of 9-aminoacridine as an indicator of pH differences artificially set across a membrane has been reexamined in liposomes prepared from bacterial phospholipids extracted from chromatophores ofRhodopseudomonas capsulata grown photoheterotrophically. The dye behaves as an ideal indicator for pH differences lower than about three units; at higher pH's the expected linear dependence of Q/(100-Q) vs. pH is no longer strictly observed. Similarly a linear dependence upon the volume of the liposomes added has been verified. The amine ceases to respond to pH changes when the pH of the external medium exceeds the value of 10, corresponding to the pK_a of 9-aminoacridine. The apparent volume of the inner phase of liposomes, as calculated from fluorescence quenching, but not the slope of dependence of fluorescence on pH, appears to be affected by several factors, including the ionic composition, the osmolarity of the external medium, and the microscopic structure of the liposomes. Millimolar concentrations of earth-alkaline cations diminish the apparent internal volume of liposomes, in agreement with the complexing effect of these ions on phospholipid bilayers. The osmotic response of the apparent inner volume has also been verified; this parameter decreases linearly with the reciprocal of the external osmolarity, as expected from the van't Hoff relation; an osmolarity exceeding 0.3 M is, however, necessary in order to observe this effect.     

Patterns of bryophyte and vascular plant richness in European subalpine springs

The diversity of spring habitats can be determined not only by local environmental conditions, but also by large-scale biogeographical effects. The effects can differ across various groups of organisms. We compared α-, β- and γ-diversity patterns of bryophytes and vascular plants of (sub)alpine springs in three contrasting mountain ranges: Alps (Switzerland), Balkans (Bulgaria), Western Carpathians (Slovakia, Poland). We used univariate and multivariate statistics to test for the effects of pH, conductivity, altitude, slope, mean annual temperature and annual precipitation on diversity patterns of both taxonomic groups and compared diversity patterns among the regions for particular pH and conductivity classes. We identified acidophyte and basiphyte, calcifuge and calcicole species using species response modelling. All regions displayed significant relationship between conductivity and α-diversity of vascular plants. Bulgaria showed the highest α-diversity of vascular plants for the middle part of the conductivity gradient. For both taxonomic groups, the β-diversity in the middle part of gradient was highest in Swiss Alps. The total species pool was lowest in Bulgaria. The percentage of basiphyte and calcicole species was highest in the Alps. In (sub)alpine springs, mineral richness was a better determinant of vascular plant α-diversity than pH, and the extent of the alpine area did not coincide with α-diversity. Observed inter-regional differences in diversity patterns could be explained by the different proportion of limestone bedrock and different biogeographic history. The differences in α-diversity between both taxonomic groups are presumably result of the different rates of adaptation processes.     

Antimicrobial efficiency and stability of two decontamination solutions

Two decontamination solutions, commercially produced BASE?128 and laboratory decontamination solution (LDS), with analogous content of antibiotic and antimycotic agents, were compared in their antimicrobial efficiency and stability (pH and osmolarity). Both solutions were compared immediately after thawing aliquots frozen for 1, 3 or 6 months. Agar well diffusion method was used to test their antimicrobial efficiency against five human pathogens: Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli and Enterococcus faecalis. The difference in the inhibition of growth between the two decontamination solutions was mostly not statistically significant, with few exceptions. The most pronounced difference between the LDS and BASE?128 was observed in their decontamination efficacy against E. coli and E. faecalis, where the LDS showed to be more efficient than BASE?128. The osmolarity value of LDS decreased with cold-storage, the osmolarity values of the BASE?128 could not be measured as they were below the range of the osmometer. Slight changes were found in pH of the less stable LDS solution, whose pH increased from initial value 7.36?±?0.07 to 7.72?±?0.19 after 6 m-storage. We verified that BASE?128 and LDS are similarly efficient in elimination of possible placental bacterial contaminants and may be used for decontamination of various tissues.     

The influence of exogenous acetaldehyde solution on the vase life of two carnation (Dianthus caryophyllils L.) cultivars in the absence or presence of exogenous ethylene

The effects of acetaldehyde concentration (0, 0.025, 0.05, 0.1, 0.2,0.3, 0.4 or 0.5%) in solution on the vase life and ethylene productionoftwo carnation (Dianthus caryophyllus L.) cultivarscontrasting in vase life (Sandrosa (long lasting) and Yellow Candy (shortlasting)) were studied. In Sandrosa, acetaldehyde solution (0.05%)increased the vase life by 3 days in the absence, or by 2 days in the presence,of exogenous ethylene; the increase in vase life was associated with a delay inthe ethylene climacteric peak. In Yellow Candy, acetaldehyde (0.05%)increased vase life by 3 days, in an ethylene free environment. In the presenceof exogenous ethylene there was no increase in vase life of Yellow Candy.Acetaldehyde failed to inhibit ethylene production in either of the cultivars.It is suggested that acetaldehyde is not involved in the inhibition of ethylenebiosynthesis or sensitivity to ethylene in these two carnation cultivars.     

Expression of Outer Membrane Proteins in Escherichia coli Growing at Acid pH

It is generally accepted for Escherichia coli that (i) the level of OmpC increases with increased osmolarity when cells are growing in neutral and alkaline media, whereas the level of OmpF decreases at high osmolarity, and that (ii) the two-component system composed of OmpR (regulator) and EnvZ (sensor) regulates porin expression. In this study, we found that OmpC was expressed at low osmolarity in medium of pH below 6 and that the expression was repressed when medium osmolarity was increased. In contrast, the expression of ompF at acidic pH was essentially the same as that at alkaline pH. Neither OmpC nor OmpF was detectable in an ompR mutant at both acid and alkaline pH values. However, OmpC and OmpF were well expressed at acid pH in a mutant envZ strain, and their expression was regulated by medium osmolarity. Thus, it appears that E. coli has a different mechanism for porin expression at acid pH. A mutant deficient in ompR grew slower than its parent strain in low-osmolarity medium at acid pH (below 5.5). The same growth diminution was observed when ompC and ompF were deleted, suggesting that both OmpF and OmpC are required for optimal growth under hypoosmosis at acid pH.     

Effects of ethylene and cytokinins on vase life of cut Eucalyptus parvifolia Cambage branches

The role of ethylene and cytokinins was investigated during postharvestsenescence of cut Eucalyptus parvifolia Cambage branches.The effect of endogenous and exogenous ethylene on the vase life of the cutbranches was studied using 2 mM 1-aminocyclopropane-1-carboxylicacid (ACC) as a continuous treatment or pulse treatment for 48h with 20, 40 and 80 l l^–1ethylene. Both endogenous and exogenous ethylene reduced the vase life of thebranches; however, the effect of the endogenous hormone was stronger than theexogenous applications. Ethylene biosynthesis was inhibited by pulse treatmentfor 24 h using 1 mM AOA or 2 mMCoCl₂. The latter treatment significantly extended the vase life ofthe branches by delaying senescence. The effect of cytokinins was evaluated onthe vase life of cut E. parvifolia branches by pulsetreatment for 24 h with 10, 50 and 100 mM thidiazuron(TDZ) or 85, 130 and 260 mM N6-benzyladenine (BA). The resultsobtained showed that no response was observed following pulse treatment with BAwhile, although TDZ had little effect on vase life, it was a good inhibitor ofchlorophyll degradation.     

The apoplastic pH of the substomatal cavity of Vicia faba leaves and its regulation responding to different stress factors.

The apoplastic pH of the substomatal cavity is an essential determinant of stomatal movement. In detached leaves of Vicia faba substomatal apoplastic pH and its dependence on external (stress) factors was investigated using a non-invasive approach: pH-microsensors were inserted into open stomata, and upon contact with the apoplastic fluid, pH was measured continuously, as apoplastic pH was challenged by changed conditions of light, atmosphere (NH(3), CO(2)), and xylem sap (abscisic acid, cyanide, fusicoccin, pH, inorganic salts). Apoplastic pH proved extremely sensitive to infiltration and local flooding, which rapidly increased the apoplastic pH by more than 1.5 pH units. Recovery from infiltration took several hours, during which light effects on the apoplastic pH were strongly impeded. This indicates that pH tests carried out under such conditions may not be representative of the undisturbed leaf. NH(3), flushed across the stomata, yielded a rapid apoplastic alkalinization from which an apoplastic buffer capacity of 2-3 mM per pH unit was calculated. Fusicoccin, fed into the xylem sap acidified the apoplast, whereas cyanide alkalized it, thus underscoring the importance of the plasma membrane H(+) pump for apoplastic pH regulation. To address the question to what extent pH was a drought signal, the effect of iso-osmotic pH changes, fed into the xylem through the petiole were tested. It is demonstrated that the apoplastic response remained below 0.1 pH per pH unit imposed, regardless of the buffer capacity. An increase in the osmolarity of the bath solution (harbouring the cut petiole) using KCl, NaCl, CaCl(2) or sorbitol alkalized the substomatal apoplast. It is suggested that pH may only act as drought signal when accompanied by elevated osmolarity.     

Characteristics of Anopheles arabiensis larval habitats in Tubu village,Botswana

Documented information on the ecology of larval habitats in Botswana is lacking but is critical for larval control programs. Therefore, this study determined the characteristics of these habitats and the influences of biotic and abiotic factors in Tubu village, Botswana. Eight water bodies were sampled between January and December, 2013. The aquatic vegetation and invertebrate species present were characterized. Water parameters measured were turbidity (NTU), conductivity (μS/cm), oxygen (mg/l), and pH. Larval densities of Anopheles arabiensis mosquitoes and their correlation with abiotic factors were determined. Larval breeding was associated with ‘short’ aquatic vegetation, a variety of habitats fed by both rainfall and flood waters and sites with predators and competitors. The monthly mean (± SE_mean) larval density was 8.16±1.33. The monthly mean (±SE_mean) pH, conductivity, oxygen, and turbidity were 7.65±0.13, 1152.834±69.171, 5.59±1.33, and 323.421±33.801, respectively. There was a significant negative correlation between larval density and conductivity (r = ‐0.839; p < 0.01), while a significant positive correlation occurred between turbidity and larval density (r = 0.685; p < 0.05). Oxygen (r = 0.140; p > 0.05) and pH (r = 0.252; p > 0.05) were not correlated with larval density. Floods and diversified breeding sites contributed to prolonged and prolific larval breeding. ‘Short’ aquatic vegetation and predator‐infested waters offered suitable environments for larval breeding. Turbidity and conductivity were good indicators for potential breeding places and can be used as early warning indices for predicting larval production levels.     

Osmotic behavior of red blood cell as seen with an ultrasonic method

We have measured the density and ultrasonic velocity (usv) of swine red blood cell (RBC) suspensions in the wide osmolarity range from 300 mOsm to 1400 mOsm in saline solution. The cellular density and compressibility of RBC at each osmolarity were obtained using the fact that the density and the compressibility are additive by volume. The osmolarity dependence of hematocrit was also measured at a constant number concentration of RBC in the range of 300 mOsm to 1700 mOsm. The cellular density and the cellular compressibility of RBC as well as the inverse of hematocrit were expressed well into one unique exponential type equation f (pi) = a [1 - b exp (-c pi)] with a common value for the coefficient c = 0.0025 against the osmolarity pi. The results were analyzed with a simple consideration based only upon the contribution of free water inside the erythrocyte through the volume concentration phi of the free water in it. According to this theoretical analysis, the density and the compressibility of the free water were found to be 0.990 g/cm3 and 4.59 x 10(-11) cm2/dyne which agree closely with 0.998 g/cm3 and 4.59 x 10(-11) cm2/dyn of pure water at 20 degrees C within the experimental error.     

betaine modulates intracellular thiol and potassium levels in Escherichia coli in medium with high osmolarity and alkaline pH

Glycine betaine stimulates the growth rate of various bacteria in high osmolarity medium. In our studies, glycine betaine stimulated the growth rate of Escherichia coli K 12 in minimal medium with normal osmolarity at alkaline pH (pH 8.2). Betaine also caused a reduction in the intracellular pools of K⁺ and low molecular weight thiols in E. coli growing both in medium with high osmolarity and at alkaline pH. These effects of betaine were absent at pH 7.0. In cells growing in high osmolarity medium, 10 mM sodium acetate or 10 M N-ethylmaleimide reduced expression of the osmosensitive gene proU to the same extent as treatment with betaine; however, under these conditions, sodium acetate and N-ethylmaleimide did not stimulate the growth of E. coli. It is proposed that low molecular weight thiols and intracellular pH may participate in the response of E. coli to betaine.